Okay, I've decided on going with 4.10's in my car, but now have a few questions about the shift points and speedometer correction. I plan on getting a Diablo Chip, which they tell me they can change the shift points and fix the speedometer for the gears with a custom tuned chip. Is this true with a 96 GT Automatic? What is a Speedcal? Will I need one if I get the chip? Are there any calculators for 4r70w's as far as rpms and mph, the only ones I can find are for 5 Speeds. Thanks!